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LostOPWiki: How to Setup Failsafe for Revo and CC3D
= How to Setup Failsafe for Revo and CC3D = It is wise to assume that the time will come when your vehicle loses radio contact with your transmitter. The term applied to how this situation is managed is referred to as Fail Safe, and as the name implies, the general approach is to configure the system to assume a state considered to be the safest, thereby reducing the chances of causing serious damage to you, the vehicle, and more importantly, other people and their property! Yes! Your safety and that of your vehicle comes second to the safety of others and their property caused by the events that could occur during such a failure. Therefore, setting up the fail safe operation is probably the most important safety step you need to perform. Most modern RC receivers have the ability to be configured to manage the loss of their controlling radio link in one of three ways each of which is discussed on this page: # Present a predefined control signal state to the flight controller for the duration of the loss of signal. In this case, the receiver is managing the fail safe. # Stop sending control signals to the flight controller all together. In this case, one must set up the flight controller to handle the fail safe. # Continue to present the last known control commands to the flight controller until radio contact is regained. It is not advised to use this option. Icon Some receivers do not have any fail safe features, and therefore it should be understood that flying with such a system is outright dangerous, and ill advised. Before continuing, you must familiarise yourself with the features of your transmitter and receiver pair. The fail safe operation of the receiver will be outlined in the user manual, and taking the time to understand it will help you choose how to manage the situation. This page serves to outline the steps and considerations to be made for the various fail safe methods. But no matter which method you choose, be sure to test it to make sure it functions as you expect. REMOVE THE PROPELLERS FROM YOUR VEHICLE WHEN SETTING UP AND TESTING FAIL SAFE. YOU WILL NEED TO ARM YOUR VEHICLE DURING THE TESTING PHASE, AND FAILURE TO ACT ON THIS ADVICE MAY RESULT IN SERIOUS INJURY. YOU HAVE BEEN WARNED! = Failure Mode = There have been many discussions, in many threads, on many different forums regarding the safest mode to assume during a fail safe condition. By consensus it is advised that for multi rotors, the safest condition is one where the throttle is cut to zero. While the results may seem catastrophic for the vehicle (and often are), it is agreed by most that this is the safest state that can be applied to the widest set of operational circumstances. It is better to let the copter fall to the ground, than to have it drift at hover throttle into a crowd of unsuspecting observers who generally don't realise just how dangerous a full set of spinning propellers can be. Spinning props under a non zero throttle condition which come in to contact with grass, branches, or other objects can also cause ESCs to burn up, short out, and conceivably cause the LiPo battery to catch fire in an unknown location. Icon Should you disagree with this view, it is advised you think carefully about using a non-zero thrust state, and give thorough and careful consideration to all possible situations that might occur while the vehicle is generating thrust in a fail safe condition. = Predefined signal state = Consulting the user manual for the RC receiver will reveal the steps involved in setting up fail safe for this method. Typically, one places all sticks, switches, and sliders on the transmitter into the desired state and then press a button on the receiver to store the control states into non-volatile memory. In the event of loss of controlling signal, the receiver will then present this state to the flight controller. Icon Here it is important to note that when employing this method, the flight controller will not be aware of the fail safe condition as the receiver is still emitting what the flight controller considers to be valid control data. In addition, it should also be noted that this modus operandi is perfectly safe and employed by many users. Once again, for multi rotors it is advised to set the system to cut throttle to zero, and allow the vehicle to fall to the ground. = Receiver stops sending signals to flight controller = The first step when using this method is to ensure that you have configured your receiver to stop sending control signals upon the loss of signal. As mentioned above, consult the user manual. Once you are confident that you have done this, power the vehicle with the flight battery so that the receiver has power. Propellers removed of course! Connect the flight controller to the GCS via a USB cable and select the System Tab. Expand the DataObjects->ManualControlCommand UAVOjvect as shown here: Take note of the value of the Connected field while you switch your transmitter on and off. For each event, you should see this value alternate between True and False. Icon Some transmitters have a lengthy power on sequence before they actually begin transmitting any signals, so bare this fact in mind and don't expect the state change from False to True to occur instantly. As this delay can sometimes be quite long, it is advised that you become familiar with the characteristics particular to your brand of transmitter. For example, some transmitters do not emit any radio control signal until all switches are placed in their default states, and the throttle stick is moved to the lowest position. If while testing the above one does not see the field change as described, then you have not set up your receiver in the manner you thought you did. Check the manual and rectify the matter. If the state remains True when the transmitter is switched off, the flight controller merely assumes the connection is still valid and will therefore not apply any fail safe operation. It will simply continue as if all is well. Do not proceed to the following steps until you have resolved the issue. Now expand the Settings->ManualControlSettings UAVObject as follows: Upon the ManualControlCommand->Connected state changing to False, the flight controller will react by applying the configured fail safe control values to each of the system control channels: Throttle, Roll, Pitch, Yaw, FlightMode, Collective, and Accessory 0, 1, & 2. Each of these channels has an associated field in this UAVObject and can be found under FailSafeChannel. Despite these field's units of measurement being indicated as a percentage (%), the valid range of values is from -1 (minumum), though zero (neutral), up to +1 (maximum). Any value entered outside of this range will be bound to these limits. Icon The most important value to take note of is the Throttle field. The default value is -1 and it is advised that it be left as such, especially for multi rotors. Fixed wing pilots have many different approaches to a fail safe set up. For example, apply values to each channel such that the vehicle's control surfaces are placed into an attitude most likely to cause the craft to spiral to the ground. The FailSafeFlightModewitchPosition field describes the Flight Mode to be applied during a fail safe condition. While this is redundant for a multi rotor since the throttle is cut to zero, a fixed wing can be switched into attitude mode for example. Values can range from -1 to 5, where -1 means that no change will be made to the Flight Mode in a fail safe condition. Values ranging from 0 through 5 correspond to Flight Modes 1, 2, 3, 4, 5, & 6 respectively. So if you want to assume Flight Mode 1 during a fail safe, then you should set this field value to zero. Flight Mode 2 corresponds to a value of 1, and so forth up to Flight Mode 6 which has a value of 5. If you have made any changes to the fields in the ManualControlSettings UAVObject, be sure to click the red up arrow at the top of the page to save them to flash. Icon The set up method for fail safe as described in this section applies also to the use of the OPLink Mini for RC control via PPM. = Last known command = Sometimes, the default state for fail safe on some receivers is one where it continues to emit the last known channel commands to the flight controller for the duration of the loss of control link. Icon This can be highly dangerous, and so for obvious reasons it is advised that one does not chose this method of operation. = Testing Fail Safe = Once you have set up your system as described above, it is essential that one tests it's operation. With the propellers removed, and flight battery inserted: # Using the transmitter, arm the vehicle in the normal fashion. # Advance the throttle to a high value and the motors will spin as if in flight. # Now switch off the transmitter. # After a short delay, the fail safe condition will be detected by either the receiver or the flight controller and the vehicle should assume the state that you have set up. Be sure that it corresponds with your intentions, and if it does not, then revise what you have done. Safe flying = Hints and Tips = Arming Timeout On the Arming Settings tab on the Input page of the GCS, there is a setting that can be applied to the vehicle whereby it will disarm after the set time if the throttle is low. Please be aware of this as it plays a factor during a fail safe condition. If the fail safe is set up for low throttle, then the vehicle will automatically disarm once the time out occurs. While for a multi rotor it is desirable that it disarm, one might not want the same for a fixed wing. So be sure to understand how your set up treats this setting. Motors Spin at Neutral On the Output page in the GCS, the check box marked "Motors spin at neutral when armed..." controls whether the motors spin when the throttle is at the low value. Be sure that you understand how your vehicle handles this state during a fail safe. Discovery Buzzer or LED It may be desirable that during a fail after a fail safe condition, a buzzer or LED is activated to aid in the locating of the downed vehicle. It is possible to place such a device on either the receiver or the flight controller such that it gets activated by the fail safe respective set up. Refer to the Adding a Buzzer to Your Vehicle page for an example on how to set up a buzzer. Using Return To Base as a Fail Safe Flight Mode For now - DON'T DO IT! There are many implications to consider before attempting to use this as a fail safe flight mode, and until such stage as the software has been extensively tested and has matured to the point that it is considered safe, it is advised that one steers clear of this choice. You can end up loosing your vehicle, as there are too many things that can go wrong for which there is undefined behaviour. For example, lets say you are flying FPV in a stabilised mode some place far away, and something happens and your copter goes into fail safe mode. You selected RTB as the flight mode, so it switches modes and starts it's journey back to base. You breath a sigh of relief, and take off your goggles and wait to catch sight of it as it returns. But what mode were you in when it lost signal? Rate Mode? Is your transmiter still switched on? Your vehicle gets closer and picks up a signal again from your transmitter upon which it returns into Rate mode, but you can't see it yet. What's it going to do? Boom! Where will you start looking? Here's another scenario: RTB flies a straight line back to base. What is in between it and the base location? Yes it will ascend to the maximum altitude attained during the flight to try and minimise the risk of hitting something, but what if it flew a maximum of 10m above the ground while you were in control and then entered fail safe because it lost RC control when you flew behind a building? Just don't do it. Also, if you really do feel passionate about using RTB as a fail safe flight mode, it is advised that one switches off the transmitter until the vehicle gets back to base, or until you can actually see it and safely fly it back. If you're lucky, when you switch on the transmitter again it will regain a signal and you can fly it down. If it doesn't get a signal, then at least you can watch it fall when the battery dies. Kategorie:LostOPWiki Kategorie:OpenPilot